The invention relates to a valve, in particular for influencing the cross section of a fluid duct.
A valve of this type is known from DE 42 23 933 A1 as a throttle device of an internal combustion engine, an electric servomotor for the throttle valve no longer lying outside the throttle duct, but instead, for cooling purposes, in this case in the intake-airstream, determined by the instantaneous valve position, through the throttle duct itself. However, because the cooling action is consequently dependent on the valve position, the motor still has to be designed again for minimum convection cooling and therefore with bulky heat exchanger surfaces, thus appreciably restricting the useful maximum cross section of the throttle duct.
Considerable torques often have to be applied for valve adjustment and then for holding the valve in its desired angular position under the load of the medium flowing up in the duct, whereas an installation of a correspondingly large-dimensioned servomotor into the interior of the duct would again reduce the useful cross section of the latter unacceptably. Consequently, an actuating shaft connected in a rotationally rigid manner to the valve and mounted in duct side walls located opposite one another transversely to the longitudinal extent usually projects out of one of the side walls to a servomotor for valve movement which is mounted outside the duct. On the other hand, an externally arranged valve drive markedly projecting beyond the outer cross section of the duct may be disturbing for the operational surroundings, particularly in the case of systems with narrow dimensioning. The space for a valve drive located outside the duct is even often not readily available particularly for the subsequent installation of such a throttle valve at an operationally predetermined point of a complex pipeline system, such as in the engine space of a motor vehicle, for regulating the air-conditioning of the passenger cell. This may then mean that a complicated, but otherwise functionally disturbing lever mechanism has to bridge the distance from the motor to the valve mounting.
Motor-moveable valves, depending on their dimensions, are used particularly in supply-air and waste-air ducts, for example for the throttling of fresh air in the air-conditioning of stationary or mobile spaces, but also, in general, for influencing the throughflow during the flow transport of flowable materials. For this purpose, the respective valve is mounted in the inner cross section of the duct about a pivot axis and can be set into different angular positions with respect to the direction of flow. When it is oriented parallel to the direction of flow, the throttle action is minimal, being forwarded only by the installation dimensions of the valve. By contrast, when the latter is oriented transversely to the direction of flow, the smallest free residual cross section remains. The geometry of the valve usually has exactly the cross-sectional form of the duct and, if necessary, depending on the flow medium, sealing lips along its circumference, so that, when the valve is oriented transversely to the longitudinal extent of the duct, the entire inner cross section of the said duct is shut off hermetically. The valve drive conventionally takes place via an electric servomotor, but, in surroundings where there is an explosion hazard, also by means of a hydraulic or pneumatic fluid motor.